Lithium-ion battery cells have seen widespread use in small consumer devices such as laptop computers and mobile telephones. Lithium-ion batteries have recently begun to supplant conventional batteries in applications having greater electrical energy demands, such as electrical vehicles and static electricity generation apparatus. Lithium-ion batteries are seeing increased use on account of their normally superior performance over conventional batteries, such as lead-acid and NiMH batteries, in particular in respect of energy storage density and power density.
To meet electrical energy demand in such larger energy demand applications a battery is typically comprised of plural lithium-ion battery cells which are arranged in at least one of series and parallel depending on current and voltage requirements.
Lithium-ion batteries can be dangerous under certain conditions on account of their containing a flammable electrolyte. Safe and effective use of a lithium-ion battery normally requires operation of the battery within its Safe Operating Area (SOA). Considering operation within a SOA further, most lithium-ion cells are damaged if discharged below a certain voltage and their lifetime is reduced if discharged at too high a current or if charged too quickly. Furthermore lithium-ion cells may be damaged if they are overcharged above a certain voltage or if they exceed a certain temperature and may burst into flames if further overcharged. In addition there is often the lesser constraint of a Normal Operating Area (NOA). Breaching the NOA results in reduction in capacity or cell life over time. These challenges are compounded by the multi-cell configuration of the typical lithium-ion battery wherein unevenness of charge and discharge can arise between cells. Careful management by way of a battery management system (BMS) is therefore normally required to provide for safe and effective operation.
Battery management systems for lithium-ion battery arrangements are known. Such a battery management system typically makes measurements of properties, such as current, voltage and temperature, in a battery and makes determinations concerning safe and effective operation based on the measurements. The determinations are often made in dependence on an analytical model of the battery.
The present inventors have become appreciative of shortcomings in known approaches to management of lithium-ion battery arrangements. The present invention has been devised in the light of the inventors' appreciation of such shortcomings. It is therefore an object for the present invention to provide an improved energy conversion arrangement comprising plural cells which are each configured to convert chemical energy into electrical energy, the energy conversion arrangement being configured to determine a condition of the plural cells. It is a further object for the present invention to provide an improved method of determining a condition of an energy conversion arrangement comprising plural cells. It is a yet further object for the present invention to provide an improved condition determining arrangement configured to determine a condition of an energy conversion arrangement comprising plural cells.